1. Field of the Invention
This invention relates to micro pH electrode assemblies for wire transmission. More particularly, this invention relates to micro pH electrode assemblies which are specially adapted for use to continuously measure by wire transmission changes in the pH of fluids in the oral cavity and to dental assemblies housing such electrodes.
2. The Prior Art
Dental research has recognized a close interrelation between dental plaque and tooth decay. It is generally accepted that dental caries are produced by the decalcification of the teeth by acids liberated by acidogenic bacteria associated with the dental plaque. Dietary sugars are readily metabolized by these acidogenic bacteria. The generation of acids starts almost immediately after food consumption.
While studies of changes in the pH of oral cavity fluids occurring after consumption of foodstuffs could indicate such foodstuffs' cariogenic potential, such measurements presently are taken only with great difficulty. One problem presented is to directly, continuously and accurately measure the particular biological phenomenon without disturbing the process to be evaluated. Wire transmission pH electrode apparatus have been used in the past with some success to measure both gross and in situ changes in the pH of oral cavity fluids (see "Evaluation of the Cariogenicity of Confectionary in Intra-Oral Wire Telemetry" by T. Imfeld, Helvetica Odontologica Acta 21, 1:1-28 (1977).
Such measurement apparatus, are, however, subject to serious limitations. The apparatus which has been used in the past generally required the space of several removed teeth from the upper and lower jaws. The apparatus is thus relatively large, difficult to wear for extended periods, and therefore can be used only with a relatively small number of potential subjects. In contrast, the reduced size, false tooth or "pontic" dental assemblies of the present invention housing the present micro pH electrode assemblies can fit into the space of only a single removed tooth. Indeed, the present "inpontic" dental assemblies (i.e., those not serving as a false tooth) can be used on subjects having a full set of natural teeth. Furthermore, due to their greatly reduced size, the present dental assemblies can be worn with comparative ease for the extended time periods necessary for the development of required bacterial plaque.
The development of micro pH indicator electrodes in the art was necessary to the development of the present dental apparatus. Such micro pH indicator electrodes are now commercially available. However, these micro pH indicator electrodes are delicate and fragile due to their small size. Thus, one problem in providing practical wire transmission assemblies employing such micro pH electrodes was the development of an appropriate flexible housing which both protected the delicate micro electrodes and also provided for wire transmission of the pH measurement. In the development of such a housing, unforeseen difficulties arose in constructing apparatus capable of continuous and accurate pH measurement. It was surprisingly discovered that moisture and ionic migration by, apparently, capillary action between the housing and both the micro electrode and the wire transmission connection plugs were responsible for short circuiting and for aberrant readings. The moisture and ionic migration problems were severely aggravated by the reduction in the size of the micro electrodes and the attendant need for close fitting protective housing. It has now been surprisingly discovered that the moisture and ionic migration can be prevented, and accurate and continuous micro indicator electrode pH assemblies can be constructed by providing a moisture and ion impermeable, plastic seal intermediate the micro electrode and its housing.